Once we get to a notion of mental content, we seem to accept readily that it is absolutely private to the person who has it. We say, "Nobody else can have my headache," or "Nobody else can have my sense impression of that chair." Let us call this the thesis of absolute privacy.

(There is also a notion of mental content, in respect of which the idea of privacy would never arise. For example, anything someone thought about. If I think about the moon that is my "mental content," and you can think about it too. My question will not be about this type of "mental content.")

Question: Is there any philosophical work that discusses and questions the thesis of absolute privacy?

Just to be clear on what I am looking for, please note:

  • The work must accept the notion of mental content as unproblematic or usable (whether because the author believes so or for an argument's sake) and explore specifically the idea that it is absolutely private or not.

  • An example may be a Frege essay, in which he imagines a mind that has certain things in it and a greater mind that has all of those (numerically identical) things plus more. This would amount to saying that mental content was not absolutely private, or that there was at least no conceptual impossibility in the idea of two minds sharing it. (I am not saying Frege was advancing this view. He mentioned something like it very briefly somewhere.)

  • A discussion of unusual brain configurations, such as two brains sharing some neural paths, may not qualify as an example if it avoids using the notion of mental content or uses it only to facilitate statement and disavows any kind of ontological commitment.

  • I am mostly interested in works in the analytic tradition. ("Analytic" here is a label sometimes contrasted with "Continental." If you don't know exactly who is analytic in this sense, you probably can't give me what I am looking for.)

  • Never mind Wittgenstein's private language argument. Of course, a work on it might go into what I am looking for.

  • I don't want to know the truth. I am only looking for published works on the topic.


Sorry, this is an off-the-cuff not-so-good answer, but too much space needed for a "comment."

When you say "mental content" such as the "headache" or chair perceptions you seem to mean "experiences," which gets into all the questions of "qualia" and such. Yet the notions of "absolute privacy" and "direct immediacy" of mind is usually based on a Cartesian rationalism that attempts to strip out our mutual immersion in sensory experiences or redescribe as form-content. I believe there are many in-betweens.

You said analytic. Hmmm. What comes to mind is something like Wilfred Sellars' priority of "intersubjective" thought over "private access" in "Empiricism and Philosophy of Mind." I believe Hillary Putnam makes a case for defining "mental content" as external rather than internal via his "twin earth" and "H20" examples. Then there's controversial work on mirror neurons and a recent case of conjoined twins partly sharing a brain reported in NYT and referenced somewhere in this stack.

You might look into works on "problem of other minds," since much philosophy has an annoying post-Cartesian habit of simply universalizing "mind" and then privatizing "bodily" perceptions. Sorry, messy, probably shouldn't have even written. But there may be something useful there.


You might consider work like 'No Boundary' by Ken Wilbur to lie in this vein. It follows down the Jungian layered Self based ultimately upon a Collective Unconcious, in detail. Of you can go straight to Jung's writings on the subject.

And you can surely find evidence that we share mental content in a more pedestrian way in modern interpretations of psychoanalytic intersubjectivity in therapeutic and other contexts. Kurt Lewin models mental space as "field", with the same sort of action-at-a-distance common to other field theories, and this perspective pays off in the understanding of group and other political action.

Active psychoanalytic group approaches like Tavistock-style group therapy trace how common issues and conditions coalesce and create shared difficulties and potential solutions (q.v. Bion). Kleinian notions like projective identification are played out particularly in the treatment of Borderline conditions (q.v. any basic course on psychoanalysis, e.g. McWilliams). Self-psychologists observe reflected impressions from transference onto shared self-objects (q.v. Kohut and Kernberg).

In a more direct way, out-of-body experiences near death or under DMT, LSD or mescaline, where people see rooms, etc from the perspectives other than their own can be taken as evidence that there is a shared constructed world from which we get information that properly only belongs to other people.

Even if we get this kind of information by reading others in some subtle way, they are unconsciously communicating it clearly enough that we can experience it as if we were living it out ourselves when we are suggestible enough. And even when we are fully aware, groups do easily manipulate us into acting on motivations that are not natively our own, without openly communicating them to us.

I am unsure how much you consider literature on these subjects to be 'philosophical work'. Hard-core psychoanalysis is surely closer to philosophy than science, but philosophers are not keen on it for the last several decades. Folks tend to admit folks like Lacan as having philosophical content, but not generally modern Transpersonalists, Jungians or Group Therapists.

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